A capacitive MEMS pressure sensor requires two electrodes that move relative to each other under an applied pressure. This configuration is most often accomplished by having a fixed electrode formed in a substrate while a moveable electrode is provided in a deformable membrane which is exposed to the pressure that is to be sensed. One or more of the electrodes are typically formed by deposition of a conductive film, electrical isolation of a conductive layer, or by simply adding a spacer layer between two conductive materials.
The formation of the moveable electrode in the deformable membrane involves a number of operational considerations such as the clamping of the membrane to set the deflection area, the impact of external stresses on membrane deflection, the impact of parasitic capacities on the membrane, the susceptibility of the membrane and clamping features to gas diffusion, and the impact of membrane over-travel on pressure sensor reliability.
A pressure sensor with a membrane configuration that accounts for the above-mentioned operational considerations is, therefore, desirable. A process for forming a pressure sensor that addresses these operational considerations is further desirable.